The dangers of eating raw fish

(CNN)Raw fish, such as sushi, and other uncooked seafood may be delicious, but they also may be dangerous — even life-threatening — if prepared inexpertly.

Case in point: A 71-year old man in South Korea developed an infection after eating raw seafood, and resulting complications required an amputation of his forearm, according to a report published last month in the New England Journal of Medicine.

The man had a history of Type 2 diabetes and high blood pressure, and he was undergoing dialysis for end-stage renal (kidney) disease. The illness developed within 12 hours of his meal and led to fever and excruciating pain in his left hand.

After two days of suffering, he visited the emergency room at Chonbuk National University Hospital in Jeonju, South Korea.

By the time he reached the hospital, a blood-filled cavity measuring 3.5 by 4.5 centimeters (about 1.5 by 2 inches) had developed on the palm of his left hand, while on the top of his hand and forearm, there was a swelling cavity under the skin.

When his doctors performed urgent surgery, they isolated Vibrio vulnificus, a bacterium commonly found in coastal ocean water, as the cause of his infection.

Vibrio vulnificus

The US Centers for Disease Control and Prevention estimates that these bacteria cause 205 infections each year nationwide. Some cases require amputations, and 15% to 30% of cases are fatal, according to the agency.

After surgery, the man received two powerful antibiotics intravenously. However, the drugs did not keep his skin lesions from worsening, and doctors performed an amputation of his left forearm 25 days after his arrival at the ER.

“The patient did well after the surgery and was discharged home,” the authors of his case report concluded.

Vibrio vulnificus — sometimes incorrectly referred to as “flesh-eating bacteria” — is one of a family of 12 bacterial species that cause sickness in humans. Symptoms of these infections can include watery diarrhea, abdominal cramping, nausea, vomiting, fever and chills. Generally, these infections do not require treatment, and severe illness is rare, according to the CDC.

About 80% of infections happen between May and October, when coastal waters are warmest, and mostly they result from eating infected shellfish, with oysters a common culprit. Still, you can also become infected if bacteria in the water enter an open wound or cut, the CDC says.

Although the South Korean patient’s amputation certainly ranks among the most hair-raising possibilities that can occur after you eat raw fish, other dangers lurk in raw or poorly cooked meals, as well.

Parasites

The growing popularity of sushi and other raw or undercooked fish and seafood dishes in Western countries has led to an increase in illness caused by anisakid nematodes (worms), according to a study published last year in BMJ Case Reports.

Anisakiasis results from eating fish or seafood contaminated with that parasite.

When the worms invade the stomach wall or intestines, the result is gastrointestinal pain, nausea and vomiting, according to the CDC. Some people develop complications, including digestive bleeding, bowel obstruction and peritonitis (an inflammation of the inner wall of the abdomen). Other people may experience an allergic reaction, including swelling, skin rash or even anaphylaxis, which can cause difficulty breathing and loss of consciousness.

Anisakiasis cannot be transmitted from one person to another and is most common in Japan, where sushi is king. Japan sees, roughly, 3,000 cases annually, according to the authors of the case study.

However, in recent years, other parts of the globe have begun to see a rise in anisakiasis illness, according to the CDC, though the agency estimates that only a case or two are reported in the US each year.

Salmonella

Raw or undercooked fish may also harbor the most common food-poisoning bacteria, Salmonella, which causes about 1.2 million illnesses, 23,000 hospitalizations and 450 deaths in the US every year, according to the CDC. Food is the source of most of these illnesses. Although raw or undercooked fish is less likely to cause a salmonella infection than other foods, including chicken and beef, it still may carry these bacteria.

Symptoms of diarrhea, fever and abdominal cramps usually develop within 72 hours after infection, and illness generally lasts four to seven days. Though most people recover from a salmonella infection without treatment, some patients experience such severe diarrhea that they need to be hospitalized.

To reduce the risk of illness caused by eating fish, the CDC recommends not eating raw or undercooked fish or squid. When broiling, boiling or cooking seafood, an internal temperature of at least 145 degrees Fahrenheit (about 63 degrees Celsius) needs to be reached to kill anything dangerous lurking beneath the skin.